Raney Cu-Nd催化剂的XPS研究

A XPS Study of Raney Copper Neodymium Catalysts

采用ＸＰＳ能谱方法和甲酸甲酯氢解反应对ＲａｎｅｙＣｕ－Ｎｄ和ＲａｎｅｙＣｕ催化剂进行了研究。发现加入适量的钕能够显著地提高甲酸甲酯氢解活性，而且合成气氢解活性略高于纯氢氢解活性，说明ＲａｎｅｙＣｕ－Ｎｄ催化剂具有一定的抗ＣＯ毒化的能力。还原后反应前样品表面铜主要是Ｃｕ０物种；在反应过程中，Ｃｕ０物种被部分氧化，而使反应后样品表面铜以Ｃｕ０和Ｃｕ＋物种存在。反应气氛不同Ｃｕ０被氧化的程度也各异，合成气气氛下表面Ｃｕ＋的百分含量明显大于Ｈ２气氛下的；由于稀土元素钕的作用，ＲａｎｅｙＣｕ－Ｎｄ催化剂表面Ｃｕ＋的百分含量小于ＲＣｕ催化剂，明显减缓了Ｃｕ０被氧化的速度，使ＲａｎｅｙＣｕ－Ｎｄ催化剂表面保持较高的Ｃｕ０分布，这可能是它具有较高反应活性的原因。

The hydrogenolysis reaction of methyl formate was investigated over Raney Cu Nd and Raney Cu catalysts using synthetic gas (33%CO+H 2) and pure hydrogen.The X Photoelectron Spectroscopy (XPS) was used for the characterization of the Raney catalysts.The reaction results showed that addition of appropriate amount of neodynium can prominently raise the hydrogenolysis activities of Raney Cu Nd catalysts,and the activity under synthetic gas is slightly higher than that under pure H 2.It illustrated that Raney Cu Nd catalysts do not suffer from the presence of CO in the reaction gases.The results of XPS indicated that the surface copper of catalysts after reduction exists as Cu 0;but some Cu 0 was oxidized during the hydrogenolysis reaction,the surface copper mainly exists as Cu 0 and Cu + after reaction.The oxidation extent of copper varied with the gas atmosphere,and the percentage of Cu + in CO+H 2 is higher than that in pure H 2.After reaction,owing to the addition of rare earth element neodymium,the surface Cu + concentration of Raney Cu Nd catalysts is smaller than that of Raney Cu;consequently,it is proved that the oxidation speed of Cu 0 was apparently slowed down and the concentration of Cu 0 was maintained higher.This is the reason why Raney Cu Nd catalysts have higher activities of methyl formate hydrogenolysis.